Novel States Induced by Superlattice Structures in Twisted Two-Dimensional Heterostructures

Two-dimensional quantum materials have attracted widespread attention due to their manifestation of numerous novel and unique characteristics. When two-dimensional quantum materials are stacked to form homojunctions or heterojunctions, variations in lattice constants and interlayer rotation angles give rise to new superlattice structures, consequently leading to a series of changes in the electronic band structures and physical properties. In this article, the discussion begins by focusing on the alterations in the lattice spatial structure and band structure resulting from the presence of the superlattice structure, such as superlattice Dirac points, Moiré excitons, and atomic reconstructions. Moreover, at specific rotation angles, the Fermi velocity of electrons will diminish at discrete angles due to the influence of the superlattice structure, giving rise to the creation of flat bands. This will cause a significant change in the physical properties of this region as they are predominantly governed by the interaction energy between electrons. These novel physical properties, arising from strong electron-electron correlations, have become one of the forefront topics in the field of condensed matter physics. Here, the article primarily focuses on subjects pertaining to strong electron-electron correlations, such as correlated insulators, superconductivity, electron crystals, and orbital magnetism. And it offers a forward-looking perspective on the future development directions of superlattice structures.